Talarazole metabolites

ABSTRACT

Novel metabolites of talarazole of formula (I) have been isolated and characterized, wherein R═H, OH, OSO3H or O-gly; R1, ═H, OH, OSO3H, O-gly or =0; and gly=a glucuronate, or a pharmaceutically acceptable salt thereof. These compounds are targeted for the treatment of various skin-, hair- and nail-associated disorders.

This application is a continuation of application Ser. No. 12/311,862,filed 29 Jun. 2009, which is a §371 of International Application No.PCT/US2007/081685, filed 17 Oct. 2007, which claims the benefit of U.S.Provisional Application No. 60/851,989, filed 17 Oct. 2006, which areincorporated herein in their entireties.

FIELD OF THE INVENTION

This application is directed to novel metabolites of talarozole(formerly referred to as rambazole). The application is also directed tothe use of these metabolites for the treatment of various skin-, hair-and nail-associated disorders.

BACKGROUND OF THE INVENTION

Talarozole((R)—N-[4-[2-ethyl-1-(1H-1,2,4-triazole-1-yl)butyl]phenyl]-2-benzothiazolamine)(formerly referred to as rambazole) is a novel enantiomerically pureretinoic acid metabolism-blocking agent (RAMBA). In preclinical in vitroand animal studies, topical talarozole has demonstrated potentialeffectiveness in the treatment of psoriasis, acne and photo-damage. Oraltalarozole is being developed for the treatment of moderate to severepsoriasis and potentially acne. See, e.g., U.S. Pat. Nos. 6,833,375;6,486,187 and 6,124,330, each of which is incorporated by reference inits entirety. Given talarozole's promise as a potent therapeutic agent,its metabolism in selected animal species was investigated and noveltalarozole metabolites were isolated and characterized. Selectmetabolites were evaluated as therapeutic agents, especially in thetreatment of keratinization-associated disorders.

SUMMARY OF THE INVENTION

An aspect of the invention is a novel isolated metabolite of talarozoleas represented by Formula I.

wherein R═H, OH, OSO₃H or O-gly; R₁═H, OH, OSO₃H, O-gly or ═O; and gly=aglucuronate, or a pharmaceutically acceptable salt thereof, with theproviso that when R═H, R, cannot also be H.

Another aspect of the invention is a compound selected from the groupconsisting of

Another aspect of the invention is the treatment ofkeratinization-associated disorders (e.g., various skin-, hair- andnail-associated disorders) in a warm-blooded mammal in need thereof,comprising administering to the mammal an effective amount of atalarozole metabolite of Formula I.

Another aspect of the invention is a pharmaceutical compositioncomprising a novel metabolite of talarozole and a diluent or carrier.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a comparison of the various talarozole metabolites acrossselected animal species.

DETAILED DESCRIPTION

Pharmaceutically acceptable salts of the metabolites of the inventioninclude the conventional non-toxic salts that are known in the art andwhich are formed by the addition of inorganic or organic acids or bases.Examples of acid addition salts include, but are not limited to,acetate, adipate, benzoate, benzenesulfonate, citrate, camphorate,dodecylsulfate, hydrochloride, hydrobromide, lactate, maleate,methanesulfonate, nitrate, oxalate, pivalate, propionate, succinate,sulfate and tartrate. Base salts include ammonium salts, alkali metalsalts such as sodium and potassium salts, alkaline earth metal saltssuch as calcium and magnesium salts, salts with organic bases such asdicyclohexylamine salts and salts with amino acids such as arginine.Also, the basic nitrogen-containing groups may be quaternized with, forexample, alkyl halides.

It is well known in the art that hydroxyl groups on chemical compoundsare subject to in vivo glycosylation. Selected isolated metabolites oftalarozole that contain one or more hydroxyl groups are evidence of thisprocess occurring in the mammals studied, including humans. In anexemplary embodiment, the glycoside is a glucuronide formed by thereaction between glucuronic acid and one or more hydroxyl groups presentin the metabolite.

In addition to carriers, the pharmaceutical compositions of theinvention may also include stabilizers and preservatives. For examplesof typical carriers, stabilizers and adjuvants known to those of skillin the art, see Remington: The Science and Practice of Pharmacy, 21^(st)ed. (Lippincott, Williams & Wilkins (2005)).

The novel metabolites of this invention may be administered alone orpreferably as a pharmaceutical formulation comprising the metabolitetogether with at least one pharmaceutically acceptable carrier.Optionally, other therapies known to those of skill in the art may becombined with the administration of the metabolites of the invention.More than one metabolite may be present in a single composition.

The metabolites of the invention are potential biological processmodulators that likely impact cell proliferation and differentiation(e.g., keratinocytes, fibroblasts, endothelial cells, sebocytes), immunefunction (e.g., hemapoeic cells) and may be used in the treatment ofskin-, hair- and nail-disorders such as, but not limited to, psoriasis,acne, actinic keratosis, eczema, rosacea, ichthyosis, alopecia andphotodamaged skin. Further, the metabolites of the invention may be usein the treatment of cancer, such as prostate cancer, basal and squamouscell carcinomas and melanoma. This invention includes methods for thetreatment of keratinization disorders in a mammal, including a human,comprising administering to said mammal an amount of the compound of theinvention or a pharmaceutical composition comprising or consisting ofthe compound of the invention, that is effective in inhibiting orarresting IP-10 dependent growth of abnormally proliferating epidermalcells, such as keratinocytes, without the addition of other therapeuticagents. In one embodiment of this method, the abnormal cell growth is atype of carcinoma, including but not limited to, basal cell carcinoma,squamous cell carcinoma. In another embodiment the abnormal cell growthis a type of melanoma.

An “effective amount” is an amount sufficient to effect beneficial ordesired results. For example, a therapeutic amount is one that achievesthe desired therapeutic effect. In an exemplary embodiment, the dailydose may range from about 0.005 to about 5 mg/kg. This amount may be thesame or different from a prophylactically effective amount, which is anamount necessary to prevent the onset of disease or disease symptoms. Aneffective amount can be administered in one or more administrations,applications or dosages.

Methods of determining the most effective means and dosage ofadministration are well known to those of skill in the art and will varywith the composition used for therapy, the purpose of the therapy, thetarget cell being treated and the subject being treated. Single ormultiple administrations can be carried out with the dose level andpattern being selected by the treating physician.

In an exemplary embodiment, the recipient of the metabolites of theinvention is a warm-blooded mammal, preferably a human.

Pharmaceutical compositions containing the metabolites of the inventioncan be administered by any suitable route, including oral, rectal,intranasal, topical (including transdermal, aerosol, buccal andsublingual), parenteral (including subcutaneous, intramuscular,intravenous), intraperitoneal and pulmonary. It will be appreciated thatthe preferred route will vary with the condition and age of therecipient, and the disease being treated.

EXPERIMENTAL

Mouse, rat, dog and human were the species used for the safetyevaluations of talarozole. More specifically, the disposition of¹⁴C-labeled talarozole was examined in mice, rats, dogs and humans afteroral administration to provide information regarding the absorption,metabolism and excretion of talarozole.

Example 1 Analysis of Talarozole Metabolites

Male and female CD-1 mice (19-29 g, n=3/sex/timepoint for bloodsampling, n=3/sex for mass balance), Sprague Dawley rats (0.205-0.237kg, n=3/sex/timepoint for blood sampling, n=3/sex for mass balance) andbeagle dogs (7-12 kg, n=3) were given a single oral dose of ¹⁴C-labeledtalarozole in 20% hydroxyl propyl B-cyclodextrin at 5 mg/kg. Healthyhuman male volunteers (76.6-107.9 kg, n=5) were dosed with a single oraldose of 4 mg ¹⁴C-labeled rambazole in ethanol. Blood samples werecollected at selected timepoints after dosing and plasma was prepared.Urine and feces were collected for 2, 7 and 8 days. For the human study,up to 288 hours post-dose and semen samples were obtained 2 and 4 hourspost-dose. Radioactivity in various matrices were measured by liquidscintillation counting (LSC). Select plasma, urine and fecal sampleswere subjected to metabolite radioprofiling and characterization, and inthe human study, semen samples. Metabolite radioprofiling wasaccomplished using HPLC with fraction collection followed by solidscintillation counting (Packard TopCount—see representative HPLC rundata below). Radioactivity peaks were integrated and the percentdistribution of individual metabolites in each sample was determined.Metabolite characterization and identification were accomplished byLC/MS (Finnigan MAT LCQ in positive or negative ESI mode) in conjunctionwith an appropriate radioactive monitor (RAM). For all species, plasma,urine and fecal samples were pooled across animals and analyzed. Plasmawas analyzed at several time-points out to 24 hours. Urine was analyzedover one time-interval (0-24 hours for mouse, 0-48 hours for rat, 0-72hours for dog, and for in the human study, 0-12, 12-24, 24-48, 0-48hours. Feces was analyzed over 2-3 time intervals (0-24 and 24-48 hoursfor mouse and rat; 0-24, 24-48, and 48-72 hours for male dogs; and24-48, 48-72, and 72-96 hours for female dogs). In the human study,feces were analyzed for 0-48, 48-96, 96-144, 144-192, 192-288, 0-144,144-288 and 0-288 hours. PK parameters for ¹⁴C-labeled talarozoleradioactivity was determined from the mean (mouse and rat) or individual(dog and human) plasma concentration versus time data. PK parametervalues were determined by non-compartmental methods using WinNonlin™.

HPLC data for separations described in Example 1:LC system: Waters 2695 Separations ModuleAnalytic column: C18 column, 4.6×150 mm, 3 μmFlow rate: 1.0 mL/minMobile phase A: 2% HCOOH in H₂O (pH 3.2)Mobile phase B: CH₃CN

Gradient:

(min) (mL/min) A (%) B (%) 0 0.7 100 0 3 0.7 100 0 28 0.7 75 25 48 0.765 35 78 0.7 30 70 83 0.7 0 100 88 0.7 0 100 90 0.7 100 0 105 0.7 100 0

Example 2 Effects on Epithelial Differentiation in Rat Vagina:Inhibition of Vaginal Keratinization Induced by Estrogenic Treatment inOvariectomized Rats by Oral Administration of Talarozole Metabolite M4

This animal model is based on the observation that retinoic acid (RA)suppresses the keratinization process in the stratified squamousepithelium of the vagina induced by estrogenic treatment inovariectomized rats (Sietsema & DeLuca, 1982; Geiger & Weiser, 1989).ED₅₀-value for complete suppression (keratinization score=0) was 1.0mg/kg/day for talarozole whereas ED₅₀-value for RA was 5.1 mg/kg/day.Oral administration of M4 during 3 days inhibited vaginal keratinizationinduced by estrogenic treatment in ovariectomized rats in adose-dependent manner. ED₅₀-value for complete suppression(keratinization score=0) by M4 was 1.2 mg/kg/day.

Example 3 Talarozole Metabolites for Suppression of IP-10 Production byIFNγ-Activated Human Epidermal Keratinocytes

IP-10, a member of the CXC subfamily of chemokines, attractsT-lymphocytes and natural killer cells. IP-10 is upregulated in, forexample, psoriasis. In particular, epidermal keratinocytes of psoriaticlesions express elevated levels of IP-10. Suppression of IP-10expression by activated keratinocytes may represent a novel target fortherapeutic intervention of inflammatory skin disorders. Talarozole, itsenanantiomer and metabolite M4 were observed to down regulatedose-dependently IP-10 expression as shown in FIG. 1.

Results and Discussion Pharmacokinetics of Radioactivity

PK parameters for ¹⁴C-labeled talarozole are shown in Table 1.

TABLE 1 Mean Pharmacokinetic Parameters of ¹⁴C-labeled TalarozoleEquivalents in Plasma Cmax AUC_(0-t) AUC_(0-∞) Species (ng Tmax t_(1/2)(hr-ng (hr-ng (0-t) Sex equiv/g) (hours) (hours) equiv/g) equiv/g) MouseMale 2633 3.0 7.6 10215 10276 (0-48 h) Female 1839 1.0 12.4 6632 6767Rat Male 1130 2.0 17.4 6720 6960 (0-48 h) Female 838 4.0 14.8 7670 7810Dog Male 2533 0.67 55.7 19555 19970 (0-168 h) Female 2719 0.67 49.021388 21902 Human Male 20.7 3.00 19.4 269 301 (0-48 h) Concentrationsare ng equivalents of ¹⁴C-labeled talarozole

Excretion of Radioactivity

In the mouse, rat and dog, over 90% recovery of the radioactive dose wasachieved after oral dosing (Table 2). The radioactive dose excreted infeces ranged from 78-89% and 78-92% in male and female animals,respectively.

TABLE 2 Percent of Dose Recovered in Excreta Species % in % in % in CageTotal % (interval) Sex Urine Feces Rinse Recovered Mouse Male 4.3 82.74.4 91.4 (0-48 h) Female 3.0 91.6 0.8 95.4 Rat Male 6.3 77.5 4.01 95.2(0-168 h) Female 10.1 77.5 3.88 95.4 Dog Male 4.1 88.7 0.8 93.6 (0-192h) Female 2.9 89.0 0.5 92.4 Human Male 7.3 72.2 — 87.7 (0-288)

It was discovered that talarozole was extensively metabolized, with themajority of metabolites excreted in the feces. In addition to unchargeddrug, 17, 26 and 19 radioactive components were observed in plasma,urine, and feces from mouse, rat and dog, respectively. Unchanged¹⁴C-labeled talarozole, M3, M4, M9 and M13 were the prominentradioactive components in mouse plasma. Rat had the greatest number ofcirculating metabolites in plasma. In addition to the metabolitesobserved in mouse, M11, M12 and M16 were observed in rat plasma. In thedog, only unchanged ¹⁴C-labeled talarozole and M4 were characterized.Unchanged ¹⁴C-labeled talarozole and M4 were the prominent metabolitesin mouse feces, accounting for 6.11 and 10.56% of the dose in male mousefeces and 7.04 and 15.16% of the dose in female mouse feces. Unchanged¹⁴C-labeled talarozole, M4, M14 and M15 were the major metabolites inrat feces, and accounted for 5.34, 4.95, 5.05 and 6.42% of the dose inmale rat feces and 4.60, 7.76, 4.82 and 2.38% of the dose in female ratfeces. M8 and M4 were the major metabolites in dog feces, and accountedfor 11.73 and 19.88% of the dose in male dog feces and 8.86 and 17.01%of the dose in female dog feces. No unchanged ¹⁴C-labeled talarozole wasdetected in mouse urine. Unchanged ¹⁴C-labeled talarozole and M4 wereobserved as minor radio-components in rat urine, accounting for0.07-1.90% of the dose. Two minor metabolites, M9 and M10, wereidentified in dog urine, accounting for 0.45-1.34% of the dose. In thehuman, talarozole was extensively metabolized. In addition to theunchanged talarozole, a total of seven metabolites were characterized oridentified. M3 and M4 were identified as monohydroxylated talarozole.M14a and M14b were proposed as dihydroxylated talarozole. M18 and M19were characterized as the glucuronides of dihydroxylated talarozole. Theprotonated molecular ion was determined for M17, but no structure couldbe proposed based on the available data. The major metabolic routes for(¹⁴C)-labeled talarozole in humans were oxidation at multiple sites,followed by glucuronidation. Based on AUC_(0-24h), unchanged talarozoleaccounted for 6.03% of the total plasma radioactivity. Three majorcirculating metabolites, M4, M14a, and M18, accounted for 27.8%, 12.8%and 10.7% of the total plasma radioactivity, respectively. M19 accountedfor 5.60% of the total plasma radioactivity. Unchanged talarozole, M4,M14a, M18, and M19 accounted for 62.9% of the total plasma radioactivitybased on AUC_(0-24h) values. Metabolite M4 was a major fecal metabolite,accounting for 16% of the dose in the human feces. Unchanged talarozoleand all other fecal metabolites were minor, accounting for less than 5%of the dose. Unchanged talarozole was not found in the 0 to 48 hourhuman urine samples and all urine metabolites accounted for <1% of thedose. Unchanged talarozole and M4 were minor radioactive components inthe semen samples and M14a was a major semen metabolite.

Metabolite Characterization and Identification

Table 3 lists the talarozole metabolites characterized and/or identifiedby LC/MS/MS. ¹⁴C-labeled talarozole was observed to metabolize to M4 viaoxidation of the benzthiazole ring, and to M3 and M13 via oxidation ofthe alkyl side change. Dioxidation of both the benzthiazole ring and thealkyl side chain yielded M14 and M15. Conjugation of M4 with aglucuronyl or sulfate moiety resulted in M9 and M16, respectively.Conjugation of M14 and M15 with a sulfate moiety yielded M11 and M12,respectively. Another metabolite route found only in dogs yielded theaddition of 162 atomic mass units (likely, a monosaccharide) to M4 or M9to provide M8 and M10, respectively.

Exemplary metabolic pathways of talarozole are proposed in the schematicbelow.

The proposed metabolic pathway of talarozole in humans is shown below:

The above description is not intended to limit the claimed invention inany manner. Furthermore, the disclosed combination of features might notbe absolutely necessary for the inventive solution. Disclosures of allpublications, patents or published applications cited herein areincorporated by reference in their entirety.

TABLE 3 Talarozole Metabolism Comparison Across Species Human (0.067mg/kg)^(a) Mouse (5 mg/kg)^(b) Plasma 0-24 h Feces Plasma 0-24 h^(e)Feces Peak Metabolite R_(t) AUC Urine % AUC Urine % Range Code ProposedStructure MW (min) (% Sample) % Dose Dose Semen (% Sample) % Dose DoseTotal Radioactivity 14C-Talarozole 211.3 ng*hr/g 7.29 80.36 9092.5ng*hr/g M 4.27 M 82.70 M (Total Collection) (100.0%) 66113.0 ng*hr/g F2.96 F 91.59 F Unidentified Metabolites from Radiochromatograms 22 peaks19 peaks 26 peaks 20 10 peaks 13 peaks 16 peaks 78.37 ng*hr/g 4.84 peaks4529.9 ng*hr/g 3.93 M 55.97 M (37.07%) (42.16%) M 2.88 F 56.69 F 2686.6ng*hr/g (40.72%) F 33 Talarozole

377 ~74 12.74 ng*hr/g (6.03%) ND  1.52 X 1377.5 ng*hr/g (15.15%) M1420.2 ng*hr/g (21.48%) F ND 6.11 M 7.04 F 28 M3

393 ~60 ND ND  1.32 ND 438.83 ng*hr/g (4.83%) M 445.29 ng*hr/g (6.73%) FND ND 29 M4

393 ~62 58.74 ng*hr/g (27.8%) ND 16.00 X 402.45 ng*hr/g (4.43%) M 492.2ng*hr/g (7.44%) F 0.02 M 0.01 F Rt not confirmed 10.56 M 15.16 F M8

555 ~44 M9

569 ~49 1937.3 ng*hr/g (21.31%) M 1208.2 ng*hr/g (18.27%) F ND ND M10

731 ~33 Rat (5 mg/kg)^(c) Dog (5 mg/kg)^(d) Plasma 0-24 h Feces Plasma0-24 h Feces Peak Metabolite R_(t) AUC Urine % AUC Urine % Range CodeProposed Structure MW (min) (% Sample) % Dose Dose (% Sample) % DoseDose Total Radioactivity 14C-Talarozole (Total Collection) 7045.6ng*hr/g M 6.33 M 77.53 M 17047 ng*hr/g M 4.13 M 88.66 M UnidentifiedMetabolites from Radiochromatograms 8995.6 ng*hr/g F 10.07 F 77.57 F18225 ng*hr/g F 2.89 F 89.00 F 14 peaks 11 peaks 22 peaks 16 peaks 13peaks 16 peaks 2505.2 ng*hr/g 3.47 M 48.90 M 9781.7 ng*hr/g  180 M 48.95M (35.56%) M 5.61 F 52.18 F (57.39%) M  168 F 43.94 F 2649.7 ng*hr/g7739.4 ng*hr/g (29.45%) F (42.47%) F 33 Talarozole

377 ~74 778.38 ng*hr/g (11.05%) M 3523.2 ng*hr/g (39.17%) F 0.10 M 1.90F  5.34 M  4.60 F 4132.9 ng*hr/g (24.24%) M 4228.0 ng*hr/g (23.20%) F ND 1.22 M  1.59 F 28 M3

393 ~60 429.53 ng*hr/g (6.10%) M 402.48 ng*hr/g (4.47%) F ND ND 29 M4

393 ~62 493.84 ng*hr/g (7.01%) 331.07 ng*hr/g (3.68%) F 0.07 M 0.29 F 4.95 M  7.76 F 3132.4 ng*hr/g (18.37%) M 6257.6 ng*hr/g (34.33%) F 0.04M 0.01 F 19.88 M 17.01 F M8

555 ~44 ND ND 11.73 M  8.86 F M9

569 ~49 312.30 ng*hr/g (4.43%) M 1084.8 ng*hr/g (12.06%) F ND ND ND 1.35M 0.45 F  4.31 M  3.09 F M10

731 ~33 0.84 M 0.64 F ND Human (0.067 mg/kg)^(a) Mouse (5 mg/kg)^(b)Plasma 0-24 h Feces Plasma 0-24 h^(e) Feces Peak Metabolite R_(t) AUCUrine % AUC Urine % Range Code Proposed Structure MW (min) (% Sample) %Dose Dose Semen (% Sample) % Dose Dose M11

489 ~36 M12

487 ~41 M13

391 ~67 406.52 ng*hr/g (4.47%) M 360.47 ng*hr/g (5.45%) F ND ND 14 M14a409 ~42 27.10 ng*hr/g 0.34 2.14 X (12.83%) 15 M14b

409 ~44 ND ND 3.02 X M15

407 ~55 M16

473 ~55 31 M17

439 ~68 ND ND 2.38 ND  7 M18 585 ~34 22.52 ng*hr/g 0.87 ND ND (10.66%) 9 M19

585 ~36 11.83 ng*hr/g (5.60%) 0.23 ND ND Rat (5 mg/kg)^(c) Dog (5mg/kg)^(d) Plasma 0-24 h Feces Plasma 0-24 h Feces Peak Metabolite R_(t)AUC Urine % AUC Urine % Range Code Proposed Structure MW (min) (%Sample) % Dose Dose (% Sample) % Dose Dose M11

489 ~36 1177.6 ng*hr/g (16.71%) M 298.32 ng*hr/g (3.32%) F ND ND M12

487 ~41 583.62 ng*hr/g (8.28%) M 268.42 ng*hr/g (2.98%) F ND ND M13

391 ~67 557.70 ng*hr/g (7.92%) M 219.16 ng*hr/g (2.44%) F ND ND 14 M14a409 ~42 ND ND 5.05 M 4.82 F 15 M14b

409 ~44 M15

407 ~55 ND ND 6.42 M 2.38 F M16

473 ~55 207.48 ng*hr/g (2.94%) M 218.47 ng*hr/g (2.43%) F 0.16 M 0.31 FRt not confirmed 1.42 M 1.33 F Rt not confirmed 31 M17

439 ~68  7 M18 585 ~34  9 M19

585 ~36

1. A method of treating a keratinization-associated disorder in a mammalin need thereof, comprising administering to said mammal an effectiveamount of a compound of Formula I or a pharmaceutically acceptable saltthereof:

wherein R is H, OH, OSO₃H or O-glucuronate; R₁ is H, OSH, OSO₃H,O-glucuronate or ═O; or a pharmaceutically acceptable salt thereof, withthe proviso that when R═H, R, cannot also be H.
 2. The method accordingto claim 1 wherein the keratinization-associated disorder is a skin,hair or nail disorder.
 3. The method according to claim 1 wherein thekeratinization-associated disorder is psoriasis, acne, actinickeratosis, eczema, rosacea, ichthyosis, alopecia or photodamaged skin.4. The method according to claim 1 wherein the keratinization-associateddisorder is ichthyosis.
 5. The method according to claim 1, wherein thecompound is selected from the group consisting of

wherein gly is glucuronate, or a pharmaceutically acceptable saltthereof.
 6. The method according to claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 7. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 8. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 9. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 10. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 11. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 12. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 13. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 14. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 15. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 16. The method accordingto claim 1 wherein the compound is

or a pharmaceutically acceptable salt thereof.
 17. The method accordingto claim 1 wherein the mammal is a human.